The present invention is directed to a mudmat foundation for supporting subsea equipment on the sea floor. More particularly, the invention is directed to a mudmat foundation which comprises a mudmat and a depending umbrella structure that confines the soil beneath the mudmat and thereby increases the bearing capacity of the mudmat foundation.
Mudmats, conductor pipes and suction piles are common types of foundations which are used to support items of subsea equipment on the sea floor. The required size of a foundation for a given item of subsea equipment is in part a function of the bearing capacity of the soil at the sea floor, which is given by the following equation:Q=faL+quA,  1where Q is the bearing capacity of the soil, f is the skin friction factor of the soil, a is the perimeter area of the foundation, L is the penetration depth of the foundation, qu is the bearing strength of the soil, and A is the bearing footprint area of the foundation.
Often the bearing capacity of the soil is unknown, and in some instances the line of demarcation between the soil and the sea water is very undefined. Under these circumstances, the subsea equipment may sink into the sea floor and become lost. In addition, as shown by equation 1, any attempt to increase the bearing capacity of the soil typically involves increasing either the perimeter area of the foundation or the bearing footprint area of the foundation, or both. However, for poorly consolidated soils, the resulting foundation may be too large to pass through the moonpool of a drilling rig or too heavy to be lifted by the standard equipment on the drilling rig.